Evaluation of Thermal Cracking Resistance of Asphalt Mixtures
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The overall objective was to develop a comprehensive model for thermal cracking analysis of asphalt concrete pavements. The proposed model aims to remedy some of the recognized limitations in the current thermal cracking models. Specifically, this effort includes the influence of oxidative aging on the viscoelastic modulus (stiffness), coefficient of thermal contraction (CTC), and strength properties of asphalt mixtures. The proposed comprehensive thermal cracking model includes four main steps: (1) asphalt pavement temperature profile prediction, (2) oxidative aging prediction, (3) thermal cracking stress calculation, and (4) thermal cracking event probability prediction. A software package termed the Thermal Cracking Analysis Package (TCAP) has been developed to assist in performing thermal cracking analysis based on the proposed model. Using TCAP, the pavement temperature, oxidative aging, and thermal stresses can be predicted at multiple depths within an asphalt concrete surface layer. Comparisons of the predicted thermal stresses with different levels of age-dependent crack initiation stress (CIS), cumulative cracking events or cracking index values can be estimated over a given analysis period. The cumulative cracking events can indicate relative thermal cracking performances of asphalt mixtures with considerations of the temperature variations, oxidative aging of the mixture including characteristic inputs such as air void level, etc. The TCAP evaluation methodology has been found to be sensitive to environmental inputs, mixture characteristics, differences in materials, and location within an asphalt pavement.